1. Field of the Invention
This invention relates to thermal management of electronics equipment, and especially, although not necessarily, to thermal management of equipment in the form of one or more printed circuit boards that are located in a cabinet, as is normally the case in computer, telecommunications or other equipment.
Because, in such equipment, a number of circuit boards may he located in a confined space, it is often necessary to provide the cabinet with a forced cooling arrangement, for example in which air is introduced into an inlet and blown or drawn through the cabinet over the circuit boards by means of a fan. In designing such equipment cabinets and the layout of the boards and any other equipment contained therein, it is clearly necessary to ensure that all components receive an adequate degree of cooling. This is not a simple task. In particular, it can be difficult to ensure that a constant supply of coolant air flows over the entire surface of the circuit boards due to the physical complexity of the interior of the cabinet.
2. Description of the Prior Art
It is known from patent specification U.S. Pat. No. 4,838,664 to check for incorrect operation of components on a circuit board by overlaying the circuit board with an overlay having thermochromic regions corresponding to the components and each such that when the respective components are at their normal operating temperatures the colours of the regions are the same, but such that if a component is over-heating or under-heating the respective thermochromic region provides a different colour.
It is also known from patent specification U.S. Pat. No. 3,889,053 to check a circuit board by coating the circuit board and also a reference circuit board with a thermochromic coating and to compare a video image of the circuit board being checked with a video image of the reference circuit board.
Furthermore, it is known from patent specification U.S. Pat. No. 4,891,250 to check the operation of individual components on a circuit board by coating the individual components with thermochromic indicators and noting the colours of the indicators in operation.
Thermochromic plates are described more generally in patent specifications GB-A-1 553 240 and U.S. Pat. No. 4,390,275, and thermochromic materials are described in more detail in patent specification GB-A-2 093 055.